Boundary layer jet interaction fluid amplifier



Jan. 6, 39%

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United States Patent US. Cl. 137-815 17 Claims ABSTRACT OF THE DISCLOSURE A fluid control device of the fluid amplifier type having no moving mechanical parts provides pressurized fluid output signals of analog or digital nature. A pair of nozzles supplied from a source of constant pressurized fluid issue a pair of initially spaced, fluid power jets in a generally similar downstream direction toward one or more fluid receivers. A control means positioned in the region between the pair of nozzles is adapted to modify the shear gradients of the pair of power jets on the near sides thereof and thereby effect two modes of fluid amplifier operation. In the first mode, the shear gradients in the adjacent boundary layers of the jets are sufliciently high to cause mutual attraction of the power jets and a resultant merging thereof. In the second mode, the shear gradients are sufliciently small to maintain the power jets in spaced relationship along the entire lengths thereof.

My invention relates to fluid control devices of the nomoving mechanical parts fluid amplifier type, and in particular, to fluid amplifiers wherein the control is achieved by controlling the interaction of adjacent boundary layers of two initially spaced fluid power jets flowing in a generally similar direction.

The recently developed fluid control devices having nomoving mechanical parts, now generally known as fluid amplifiers or fluidic devices, are daily becoming more important. The advantages of the fluid amplifier are numerous and may be briefly summarized as relatively simple in design, inexpensive in fabrication, capable of withstanding extreme environmental conditions such as shock, vibration, nuclear radiation, high temperatures and the no-moving parts feature permits a substantially unlimited lifetime thereby achieving long periods of uninterrupted circuit operation. These devices may be employed as digital and analog computing elements and also as power devices to operate pistons, valves and the like.

Two basic types of fluid amplifiers exist, the first being commonly referred to as the momentum exchange type wherein a main or power fluid jet is deflected by one or more control jets directed laterally at the power jet from opposite sides thereof. The power jet is normally directed midway between two fluid receivers and is deflected relative to the receivers by an amount proportional to the net sideways momentum of the control jets. This type is therefore commonly referred to as a proportional or analog device.

The second basic type of fluid amplifier is generally known as a boundary layer or Coanda effect device wherein the power jet and control jets interact in a chamber having two particularly designed divergent sidewalls. The effect of the interaction chamber sidewalls is such that the power jet attaches to one or the other of the sidewalls but not to both sidewalls at one time and the power jet switches to the other sidewall generally only upon the supply or removal of a control fluid jet. Since this second type of fluid amplifier is basically a two position device, it is generally referred to as a digital device.

Although the above described analog and digital fluid amplifiers may be satisfactory for many applications, there are instances wherein their use is not completely satisfactory due to their inherent noise level and relatively low gain.

Therefore one of the principal objects of my invention is to provide a new type of fluid amplifier which is operable on the concept of boundary layer jet interaction.

Another object of my invention is to provide a new type fluid amplifier wherein the boundary layer jet interaction is obtained by modifying the shear gradients of two spaced power jets flowing in a similar direction.

A further object of my invention is to provide a new type fluid amplifier of the proportional output type but which is not operable on the concept of momentum exchange between power and control jets.

A still further object of my invention is to provide a new type fluid amplifier of the digital output type but which is not operable on the concept of power jet attachment to side walls of an interaction chamber.

Briefly stated, my invention provides fluid control devices having no moving mechanical parts and which are adapted to provide an analog or digital pressurized fluid output. The device comprises a pair of nozzles supplied from a common source of constant pressurized fluid and adapted to issue a pair of initially spaced fluid power jets in a generally similar direction toward a fluid receiving means which may comprise one or more fluid receivers. One or more control nozzles are positioned between the two power nozzles and are adapted to issue control fluid jets or effect a subambient pressure region between the power jets for modifying the shear gradients in the boundary layers of the power jets on the near sides thereof. The fluid amplifier is operable in two modes, the first mode being wherein the shear gradients in the adjacent boundary layers are sufliciently high to cause mutual attraction of the power jets and the resultant interaction of the boundary layers causes merging of the two power jets into a single jet. In the second mode of operation, the shear gradients are sufficiently small to maintain the p0wer jets in spaced relationship along the entire lengths thereof. The devices are operable as analog or digital devices, analog operation being performed generally in the first mode by varying the point of merger of the power jets.

The features of my invention which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference character, and wherein:

FIGURES 1a, 1b illustrate top views of two embodiments of a single receiver fluid amplifier constructed in accordance with my invention;

FIGURES 2a, 2b illustrate two embodiments of the fluid amplifier of FIGURES 1a and 1b but having a nonparallel orientation of the power nozzles;

FIGURES 3a, 3b, 3c illustrate three embodiments of a two receiver fluid amplifier having a common output and center vent;

FIGURE 4 illustrates another configuration of the control fluid input portion of my fluid amplifier;

FIGURE 5 illustrates a two receiver fluid amplifier provided with two control nozzles;

FIGURES 6a, 6b, 6c illustrate three embodiments of fluid amplifiers having at least three receivers interconnected to provide two outputs;

FIGURES 7a, 7b illustrate two embodiments of fluid amplifiers especially adapted for digital output; and

FIGURE 8 illustrates a venting arrangement for the control jet which may be used in any of the above described embodiments.

Referring now to FIGURE 1a, there is shown a diagrammatic view in top plan of a fluid amplifier device constructed in accordance with my invention and especially adapted for use as an analog device to provide a proportional or analog type pressurized fluid output in response to a pressurized fluid input which would generally be analog in nature although it may be digital. The device represented as a whole by numeral 10, comprises a plurality of confined, symmetrically disposed passages for the flow of a fluid which may be a liquid or gas, including air, and these passages may be formed by any suitable method in any' solid material that is nonreactive with the fluid medium employed, as in the case of conventional momentum exchange and boundary layer type fluid amplifiers. As in the case of conventional fluid amplifiers, one (or two) parallel disposed cover plates are employed to confine the fluid to the various passages and each passage is preferably rectangular in cross section.

One of the novel aspects of my invention is to provide a pair of power fluid restrictors (nozzles) 11 and 12 which are connected by means of suitable fluid passages to a common source 13 of constant pressurized fluid. Nozzles 11 and 12 are oriented in parallel relationship and are spaced sufiiciently apart to cause the issuance of two initially separated (power) jets (11a and 12a, respectively, shown in dotted outline) of the pressurized fluid from the nozzles. A gradual decrease in dynamic pressure and velocity of each power jet with increasing distance axially and downstream from the nozzle is caused by a gradual expansion of the jet in its boundary layer in accordance with basic fluid dynamics principles. For assumed equal dimensioned power nozzles 11 and 12, each power jet has an identical velocity profile and shear gradient characteristics at the same distance axially from the nozzles. The lateral spacing between nozzles 11 and 12 is sufficiently small and the axial spacing between the nozzles and a fluid receiving passage (receiver) 14 is sufficiently large such that the boundary layers by natural entrainment of stagnant fluid adjacent the near sides of the two initially spaced parallel power jets, create a low pressure region between them and hence mutual controllable attraction between the two jets. This mutual attraction of the two jets, hereinafter described as a boundary layer jet interaction, is a function of the shear gradients of the power jets on the near sides thereof. For sufliciently high shear gradients, the mutual attraction results in a merging of the jets at some point 22 downstream from the nozzle exits. This merger of the power jets is the first of two stable operating modes of my device. The velocity profile of the merged power jets at the entrance to receiver 14 in relation to the centerline axes of the power nozzles is illustrated in the upper of the two curves below device in FIGURE 11:. This (dotted outline) plot indicates that the velocity (and .pressure) midway between the two centerline axes is at a maximum and that at the centerlines the velocity (and pressure) are substantially reduced from such maximum and have a relatively high shear gradient (the slope of the velocity profile plot).

Vent passages 15 and 16 are disposed between the exit of power nozzles 11, 12 and receiver 14 on the far sides of the power jets. The vent passages relieve fluid pressure in receiver 14, especially under blocked load conditions in the receiver output which comprises a widening passage and output passage 17 (shown circular to indicate its passing through the cover plate). The load (not shown) may comprise any suitable device such as another of my novel fluid amplifiers described herein, a conventional type fluid amplifier, a valve, or a piston in a cylinder. The upstream walls of the vent passages may be perpendicular to the nozzle centerline axes, but preferably are disposed at a greater divergence (as illus- 4 trated) to insure that the power jets do not tend to diverge from their centerline'axes immediately adjacent the nozzle exits.

The first, or merged mode of operation of my device, is maintained until such time that the shear gradients of the power jets are sufficiently decreased. For purposes of modifying the shear gradients and thus changing the boundary layer interaction of the two power jets, a control means is positioned between the two power nozzles 11 and 12. In FIGURE 1a, the control means comprises a single control nozzle 18 positioned midway between the two power nozzles and thus having a centerline axis coincident with the centerline axes of receiver 14 and device 10. The width of control nozzle 18 is generally (although not necessarily) less than the width of the power nozzles and in many application is considerably smaller in width. Control nozzle 18 is connected by means of a suitable fluid passage to a source 21 of fluid pressurized above ambient and which may comprise the output of a previous stage of fluid amplifiers or other device adapted to provide a fluid pressurized in accordance with a particular control system parameter or other information. Thus, source 21 may provide fluid under varying pressures (analog type input signal), or of the on-ofi pulse type (digital type input signal).

The control effected by operation of the control nozzle 18 will now be described. A control jet issuing from control nozzle 18 is directed into the space between the power jets. With gradual increase in pressure of the control jet, the shear gradients along the near (adjacent) sides of the power jets gradually decrease to thereby decrease the mutual attraction of the jets and move the point of jet merger 22 further downstream along the centerline axis. Upon a sufficient increase in control fluid pressure the merger point 22 is shifted beyond receiver 14 and the power jets 11b and 12b (shown in dashed outline) are in spaced relationship along the entire lengths thereof. The second, or separated mode of operation of my device occurs when the shear gradients at the near sides of the power jets have been reduced beyond a particular level determined by the relative size and spacing of nozzles and receiver. The velocity profile of the jets at the entrance to receiver 14 in the separated mode of operation is indicated in the lower of the two plots depicted below device 10 in FIGURE 1a. This (dashed outline) plot indicates that the peak velocity (and pressure) magnitudes corresponding to the power jets have shifted away from the receiver centerline, and thus a much lower pressure'is recovered in receiver 14 and output passage 17. The degree of shift of the peaks in the velocity profile is, of course, a function of the control pressure relative to the power fluid pressure, a greater control pressure causing a greater separation of the jets and greater shift of the peaks. The valley or minimum between the peaks, along the receiver centerline, obviously also increases in magnitude with increased control pressure. A minimum output pressure in passage 17 is obtained, for a given set of conditions, at a particular value of control fluid pressure which is effectively a compromise between the maximum power jet separation etfect with resultant shift of the maximum amplitudes of the jet profile away from the receiver centerline, and the increased pressure along the centerline due to the increased control jet pressure. Thus, it is evident that the velocity (and pressure) profile of the fluid jets in the region of the receiver and some distance upstream thereof is radically modified by the presence of the control jet. This phenomenon is further illustrated by comparison of the boundary layers of the power jets, the dotted outlines 11a, 12a indicating the boundary layers of the power jets in the merged mode of operation and the dashed outlines 11b, 12b representing such boundary layers in the separated mode of operation.

The operation of my FIGURE la device is seen to provide a proportional or analog variation of the output pressure AP in the receiver 14 (and output passage 17) in response to a pressure varying control input signal AP provided from supply 21 and thus provides amplification AP /AP which is linear over a particular range of operating pressures. In particular, linear operation is obtained in the merged mode by varying the merger point 22 along the device centerline axis. High gain (amplification) is obtained since the merger point 22 (and output pressure) is varied with small changes in control pres sure. Since the FIGURE 1a device has only a single receiver and control nozzle, the (control) input and output are necessarily single-sided. Also, signal inversion occurs since an increased control (signal) pressure decreases the output pressure and vice versa within the normal operating range of my device.

FIGURE 1b illustrates a modification of the amplifier illustrated in FIGURE la in that the power nozzles 11 and 12 are spaced apart a greater distance. In addition, the pressure of the control fluid available at supply 21 is below ambient rather than above as in the case of the FIGURE 1a embodiment. Thus, the presence of a control signal at control nozzle 18 causes a suction or reduced pressure rather than the increased pressure caused in the FIGURE 1a embodiment. Due to the wider spacing of the power nozzles, the power jets (11a, 12a shown in dotted outline) in the absence of a control signal are in separated mode, impinge upon the downstream walls of the vent passages 15, 16 some distance from receiver 14, and exhaust through the vents whereby no output (a binary ZERO signal) appears in the receiver and output passage 17. Upon the application of a sufliciently low subambient pressure control signal, the power jets attain the merged mode and a pressurized output (a binary ONE signal) appears in the receiver 14 and output passage 17. The velocity (and pressure) profile of the jets is indicated below device for the separated and merged modes wherein the separated mode is indicated by dotted outline and the merged mode by the dashed outline. Thus, the FIGURE lb embodiment is especially well adapted for digital operation wherein the output signal is of the on-off type.

For digital operation the FIGURE 1b device is supplied with a digital type (pulse) control signal such that no output signal appears in output passage 17 when the control signal is at zero pressure (ambient) and a pressurized output signal (above ambient) appears upon application of a control pulse having a pressure magnitude sufliciently below ambient to cause merger of the two power jets along the device centerline axis in a region upstream of receiver 14.

Comparison of the FIGURES la andlb embodiments indicates that the operation of my two-power jet boundary layer jet interaction fluid amplifier is determined primarily by the following geometrical factors (1) receiver width (2) spacing between power nozzles (3) axial distance between power nozzles and receiver, and (4) the ratios of factors 1, 2 and 3 with respect to each other. Thus, the FIGURE 1a embodiment which was described as analog in operation, is converted to a digital type fluid amplifier by (l) spacing the power nozzles further apart as illustrated in FIGURE lb or (2) by decreasing the axial distance between the power nozzles and receiver. In like manner, the FIGURE lb device is converted to an analog device by (l) spacing the power nozzles closer together, (2) possibly 'by increasing the power nozzlereceiver axial distance or (3) increasing the width of the receiver. Although the power fluid has been described as being supplied from a source of constant pressurized fluid, it is to be understood that such supply, especially in the case of digital amplifier operation, need not be constantly pressurized but may actually be one of two digital (logic) input signals, the other logic input signal being provided from the control fluid supply. In this latter case, binary logic functions such as an AND gate may be obtained. It is also evident that by proper sizing of the nozzles and vents a memory function is obtained in that if the power jets are in the merged or separated mode, they remain in their respective modes until an appropriate control signal is applied. The following ranges of dimensions for the various parameters form a preferred embodiment of my invention (but my invention is not limited thereto), and these ranges are applicable to all the embodiments herein described. The receiver Width is equal to, or greater than, the sum of the widths of the two power nozzles and less than three times their sum, and, the power of the control jet is much less than the power of each power jet wherein the power is defined as the rate of fluid flow times the pressure (drop) of the fluid through the nozzle. The control pressure may be equal to, greater or smaller than the power pressure depending upon the particular application.

FIGURE 2a illustrates another embodiment of my two power jet, single receiver fluid amplifier and is distinguished from the FIGURES 1a and 1b embodiments in that the axes of the power nozzles are not parallel but are oriented in convergent relationship. The convergent relationship of the power nozzle axes establishes the power jet merger point 22 closer to the power nozzles (merged mode shown in dotted outline) than in the case of the FIGURE la embodiment for power nozzles having equal spacing therebetween. It is obvious that for reasonable axial spacing between the power nozzles and receiver, the operation of the FIGURE 2a embodiment is similar to that of the FIGURE 1a device, the primary distinction being that the pressure magnitude of the control jet must be greater than in the FIGURE 1a embodiment for causing separation of the merged power jets. Thus, the operation of the FIGURE 2a embodiment is also analog in nature since there will always be some output in receiver 14, however, the gain AP /AP, is lower since a greater control pressure is required to modify the shear gradients of the power jets and move merger point 22 along the centerline axis. The plots below the device 10 indicate the velocity profile in the merged mode (dotted outline) and separated mode (dashed outline) for the same values of power and control pressures as in the FIGURE 1a device. Note the sharper velocity (and pressure) peak in the merged mode and the: closer spacing of the peaks in the separated mode due to the greater mutual attraction effected by the power jets issuing from convergently disposed nozzles.

In like manner, the FIGURE 2b embodiment is similar in operation to the FIGURE lb embodiment in that it is in the most general case digital in nature. The FIG- URE 2b device utilizes a divergent orientation of the power nozzle axes to provide two power jets which, in the absence of any control fluid action, issue in diverging relationship (shown in dotted outline) impinging on the downstream walls of vent passages 15 and 16 and providing no output in receiver 14. A pressurized output is obtained in receiver 14 and output passage 17 upon the application of a sufficiently low subambient pressure at fluid supply 21 to cause the merged mode of operation of the power jets. Due to the nonparallel orientation of the power nozzles, digital action may be achieved by a closer spacing of these nozzles than in the FIGURE 1b embodiment. It should be emphasized that in all my singlesided devices, digital operation does not imply that all of the jets fluid flow must pass into the receiver in the merged mode of operation. The only requirement is that in the separated mode substantially no fluid enters the receiver. The angles of the power nozzle axes in the FIG- URES 2a and 2b embodiment relative to the device centerline axis are preferably in the range of or 3 to 15 degrees. As in the case of the FIGURE lb embodiment, the FIGURE 2b device can be converted to an analog device especially for the smaller divergent angles of the power nozzle axes.

FIGURES 1a, lb, 2a and 212 each illustrate a single receiver fluid amplifier device constructed in accordance with my invention. FIGURE 3a illustrates a two-receiver device having a center vent V passage as well as the side vents 15 and 16. Receivers 31 and 32 are oriented substantially in alignment with the axes of parallel power nozzles 11 and 12, respectively. Center vent 33 is aligned with the centerline axis of the fluid amplifier device which coincides with the. control nozzle 18 axis. Receivers 31 and 32 are connected by suitable widening passages to a common output passage 17. The receivers, vents and nozzles are symmetrically disposed about the centerline axis of the device in this, and all other embodiments herein disclosed, although for certain applications a nonsymmetry may be desirable, and thus my invention is not limited to a symmetrical arrangement. The velocity profile of the fluid jets illustrated at the lower part of FIGURE la is also applicable to the fluid jets in the FIGURE 3a embodiment, the vertical axes now representing the centerline axes of the power nozzles and receivers. Obviously the receivers need not be aligned with the power nozzle axes, and such receivers can be spaced further apart or closer together as determnied by the particular operating (input-output signal) characteristics desired. The spacing between the power nozzles and the axial distance between power nozzle and receivers is such that the two modes of operation obtained for the FIGURES 1a and 2a embodiments are also obtained in the FIGURE 3a embodiment. Thus, in the absence of a control fluid flow, the two power jets (shown in dotted outline) issuing from nozzles 11 and 12 merge in the region at point 22 and in the presence of a gradually increasing pressure control fluid flow, the power jet merging point 22 moves along the centerline axis toward vent 33 until the control fluid pressure is suflicient to cause separation of the power jets. The maximum output pressure is recovered in the receivers for the control pressure wherein the peaks of the velocity profile in the separated mode are centered on the receivers. A further increase in the pressure of the control jet spreads the power jets further apart but also increases the pressure level between the power jets as a result of pressure builtup from the control jet. Thus, the pressure of the output signal in the receivers and output passage 17 varies proportionally with the control fluid pressure and linearly therewith over a particular range of operating pressures whereby device is an analog type device.

FIGURE 3b is a second version of a two-receiver, center vent fluid amplifier device constructed in accordance with my invention, the particular distinction being that the power nozzle axes are oriented in convergent relationship similar to that illustrated in the FIGURE 2a embodiment. The two mode operation of the FIGURE 3b device is identical with the operation of the FIG- URE 2a device inthe region upstream of the receivers 31, 32, the distinction occurring in the means for recovering the output signal which was adequately described with reference to FIGURE 3a. The convergent relationship of the power nozzle axes limits the operation of the device to the analog type as in the case of the FIGURE 2a device.

FIGURE 30 illustrates a third verison of my tworeceiver, center vent device wherein the power nozzle axes are oriented in divergent relationship as in the case of the FIGURE 2b embodiment. The FIGURE 3c embodiment is therefore also particularly well adapted for digital operation although analog operation may also be obtained especially for the smaller angles of divergence of the power nozzle axes, as described with reference to the FIGURE lb device. The angle of divergence of the power nozzle axes and the orientation of the receivers 31, 32 is such that the power nozzle axes intersect the downstream walls of vent passages 15, 16 at some distance from the receivers 31, 32. The two mode operation of the FIGURE 3c embodiment is identical with the operation of the FIGURE 2b device in the region upstream of the receivers, the distinction occurring in the means for recovering the output signal which was adequately described with reference to FIGURE 3a. The receiver widths in the FIGURE 30 device are preferably smaller than the receiver width in the FIGURE 2b device to insure that substantially no fluid enters the receivers in the separated mode of operation of the device as a digital device (shown in dotted outline).

FIGURE 4 illustrates an embodiment of the tworeceiver, center vent device which is identical in operation to the FIGURE 3a embodiment. The primary distinction in the FIGURE 4 embodiment is in the control means. The control means for determining the mode of operation and for varying the merger point 22 along the centerline axis of the device comprises a fluid passage having its input end (not shown) in communication with a pressurized control fluid source and having its output end 44 passing through the top or bottom cover plates of the device and in communication with a region immediately downstream of a semicircular power fluid flow splitter 43. The output end 44 may be an enlarged aperture rather than a flow restrictor or nozzle. The control fluid issuing from aperture 44 is directed toward center vent 33 by the entrainment action of the power jets which flow along opposite sides of control fluid aperture 44. The power jets issue from nozzles 41, 42 formed on one side by flow splitter 43 and on the other side by diverging ends of passage 40 in communication with supply 13. The FIGURE 4 embodiment, as the FIGURE 3a device, is especially well adapted for analog operation and the description of its two mode operation is the same as for the FIGURE 3:: device. The merged mode of the power jets is indicated in dotted outline. Digital operation of the FIGURE 4 embodiment may be obtained as described earlier with reference to FIGURE 1a, or by orienting the nozzles 41 and 42 in divergent relationship such that in the absence of any control fluid action the two power jets remain separated and impinge on the downstream walls of side vents 15 and 16 at some distance from the receivers to thereby provide substantially no output therein. Upon application of a sufliciently low subambient pressure in control fluid passage 44, the two power jets become merged to provide an output in receivers 31 and 32.

FIGURE 5 illustrates an embodiment of my device similar to the FIGURE 3a embodiment in that it also employs two receivers and a center vent, however, the two receivers 31 and 32 do not have a common output but instead are provided with separate outputs 50 and 51, respectively. In addition, the control means comprises two symmetrically disposed control fluid nozzles 52 and 53 which are supplied from one or two sources of pressurized control fluid. The control fluid source, in general, provides a double-sided (difierential) pressurized fluid signal which may conveniently be obtained from a prior fluid amplifier stage. The double-sided control fluid signal permits a nonsymmetrical control of the power jets such that a double-sided output signal may be obtained in the receivers and output passages 50 and 51. Thus, in the case wherein no control fluid issues from nozzles 52 and 53 or the pressures thereof are equal and of relatively low magnitude, the two power jets are symmetrically directed toward the receivers and remain in their merged mode (assuming sufficiently small spacing between power nozzles) remain in their merged mode. Increasing the pressure of the two control fluid jets equally above a predetermined value obtains the separated mode but maintains a symmetrical distribution of the power jets. However, varying the pressures of the two control jets unequally produces a nonsymmetrical distribution of the power jets. Thus, increasing the pressure of the control fluid issuing from nozzle 52, and decreasing the pressure of the fluid issuing from nozzle 53 causes the two power jets to tend to converge toward receiver 31 whether in the merged (shown in dotted outline) or separated modes. In like manner, a differential control signal which increases the pressure of the control fluid issuing from nozzle 53 and decreases the pressure of the fluid issuing from nozzle 52 causes the two power jets to tend to converge toward receiver 32. Thus, it is evident that a double-sided (diflerential) output proportional to the diflerential control input is attained with my FIGURE embodiment, resulting in an analog type device. My FIGURE 5 device is most generally operable as an analog device in the merged jet mode by varying the merge point 22 location, but is also operable as such by successive operation in both modes, as in the case of all of my analog device embodiments.

FIGURE 6a illustrates a device similar to FIGURE 3a embodiment but employing an additional pair of outer receivers 60 and 61 connected through suitable passages to a second common output 62. The orientation of the receivers with respect to the power nozzles may be varied but a preferred embodiment has the centerline axes of the power nozzles aligned with the center of inner receivers 31 and 32. For a particular spacing of the power nozzles 11 and 12 and their parallel disposition, it is assumed that the power jets remain merged (shown in dotted outline) in the absence of a sufliciently high pressurized control fluid jet issuing from nozzle 18. Thus in the merged mode of operation, a higher pressurized output is obtained in receivers 31 and 32 and output 17 than in receivers 60 and 61 and output 62. Increasing the pressure of the control fluid flow gradually separates the power jets and provides a proportionally increasing pressurized output in receivers 60 and 61 and a proportionally decreasing output in receivers 31 and 32, or varying the control pressure while operating in the merged mode changes the position of merge point 22 along the device centerline axis, to thereby obtain analog operation.

In the FIGURE 6b embodiment, the inner pair of receivers and center vent of FIGURE 6a are interchanged such that the FIGURE 6b embodiment has a center receiver 63 and first output passage 64, a pair of vent passages 65 and 66 and a pair of outer receivers 60 and 61 connected to a second output passage 62. The centerline axes of the power nozzles 11 and 12 are aligned with the center of vents 65 and 66 in a preferred embodiment of this device although it is recognized that other orientations may be employed-depending upon the particular operating characteristics desired. The FIGURE 6b embodiment provides a greater range of linear operation than the FIGURE 60 embodiment due to the increased spacing of the receivers and the location of vents 65, 66 therebetween. In other respects the FIGURE 61) embodiment is similar in operation to the FIGURE 6a embodiment.

FIGURE 6c illustrates a third version of my device employing five fluid passages downstream of the power nozzles. The receivers and vent(s) comprising the five passages may be interconnected as shown in FIGURE 6a, or as in FIGURE 6b, the chief distinction being that a pair of control fluid nozzles 52 and 53 are symmetrically disposed between the powernozzles 11 and 12 as in the FIGURE 5 embodiment and are operable in the same manner as shown by the'me'rged jets in dotted outline. The passages connecting the receivers 31', 32 and 60, 61 to the output passage 17 and 62, respectively, are arranged in downstream convergent relationship, as shown, to prevent backflow into the lower pressurized receivers (32, 61) when the jets are nonsymmetrically disposed as shown. The FIGURES 6a and 6b devices provide twosided output signals for single-sided control input signals whereas the FIGURE 6c device provides the two-sided output signal in response to a two-sided control input signal supplied to nozzles 52 and 53. Thus, the FIGURES 6a, 6b and 60 devices are each capable of analog type operation. Obviously the power nozzles in each of these embodiments may also be disposed with their centerline axes in a convergent relationship or in divergent relationship as required to obtain desired operating characteristics.

FIGURES 7a and 7b illustrate two embodiments of my device which are particularly adapted for digital operation. The particular control means and power jet generating means (in FIGURE 7b) have been described in detail hereinabove (with respect to FIGURE 4). A pair of spaced receivers 31 and 32 are disposed downstream of the two power jet generating means. Between the two receivers is positioned a symmetrical flow deflector 72 comprising a first portion of two curved side walls 73 having a juncture and a second portion of side walls 74 defining the inner sidewalls of receivers 31 and 32. The power nozzles are spaced apart and oriented with respect to the receivers such that in the absence of any control fluid action, the power jets impinge, at least in part, on receivers 31 and 32 and are maintained in the separated mode. Upon application of a subambient pressure of sufficiently low pressure magnitude at control fluid supply 21 (and aperture 44) the two power jets are merged such that the merged jet (shown in dashed outline) impinges entirely on the curved surfaces 73 of flow deflector 72 and is thereby deflected through side vents 15 and 16, providing no output in output passage 17. Thus, digital (onoff) type operation is obtained. Obviously analog type operation may also be obtained by the proper proportioning of the various dimensions and orientations of nozzles and receivers. The FIGURES 7a and 7b embodiments are also operable in a digital and analog mode of operation when utilizing control fluid pressurized above ambient by proper proportioning and orientation of the various elements such as by extending the curved surfaces 73 of the flow deflector a greater distance outwardly from the device centerline, or obtaining closer spacing between the two power nozzles such that on application of a sufliciently high pressure control jet the power jets are separated and impinge, at least in part, on receivers 31 and 32 to provide a pressurized output in passage 17.

In each of the hereinabove described embodiments, a venting arrangement may also be provided in the control fluid means to isolate changes in the output from refiushing back into the signal (control) passages. As illustrated in FIGURE 8, indentations and 81 on both sides of the control fluid nozzle 18 can be provided and suitable passages 82 and 83 are located therein which are in communication with the ambient to provide venting to the ambient, or may be connected back to the fluid supply, as desired.

From the foregoing description, it can be appreciated that my invention provides a new fluid control device of the fluid amplifier type having no moving mechanical parts and which is adapted to provide analog or digital pressurized fluid output signals. The digital embodiment of my invention has utility in binary logic computing circuitry and other types of fluidic logic circuits while the analog embodiment is especially useful in providing amplification of low pressure level signals. The features of low cost due to the variety of materials from which the device may be constructed and the inherent long life due to the absence of any mechanical moving parts makes these devices highly desirable in fluid power and control applications, and the high gain of the analog embodiment is an especially desirable feature.

Having described several embodiments of my two power jet boundary layer interaction fluid amplifier it is believed obvious that modification and variation of my invention are possible in the light of the above teachings. Thus, the means for generating the two power jets may comprise structure other than that first illustrated in FIG- URES 1a and 4, the only criteria being that a pair of initially spaced power jets are directed in a generally similar direction toward the receivers and are disposed relative to each other such that they can be maintained in a merged state or separated state depending upon the control eifect provided between the power jets. Thus, the two power nozzles may be supplied from two different sources of constantly or intermittently pressurized fluid to obtain outputs representing various analog and digital functions.

Finally, although all of the illustrative embodiments disclose a symmetrical arrangement of equal width power nozzles and equal width receivers, it is to be understood that such symmetry and equal widths is not a necessary condition for the successful operation of my invention and in some cases, especially in the case of the logic type digital ampliefirs, a nonsymmetry and/ or unequal widths may be necessary to provide the desired logic function.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fluid control device having no mechanical moving parts and comprising first means for generating a pair of initially spaced jets of fluid directed in a generally similar direction, fluid receiving means downstream from said first means for receiving fluid from the jets generated by said first means, and active control means positioned adjacent said first means for modifying the shear gradients of the pair of jets on the near sides thereof to thereby provide device operation in either of two modes and thereby control the fluid received by said fluid receiving means wherein the first mode the shear gradients in the adjacent boundary layers of the jets are sufl'iciently high to obtain mutual attraction of the jets and resultant merging thereof, and in the second mode the shear gradients are sufliciently small to maintain the two jets in spaced relationship along the entire lengths thereof. 2. The fluid control device set forth in claim 1 wherein said control means is adapted to provide a stream of pressurized fluid between the pair of initially spaced fluid jets to vary the shear gradients thereof and thereby vary the proportion of pressurized fluid received by said fluid receiving means by varying the merger point of the jets in the merged mode of operation, and venting means disposed on the far sides of the pair of jets for relieving fluid pressure in said receiving means. 3. The fluid control device set forth in claim 1 wherein said control means is adapted to intermittently provide a stream of fluid of constant pressure between the pair of initially spaced fluid jets to intermittently vary the shear gradients thereof sufficiently such that in the first mode the merged jets are directed to said fluid receiving means and in the second mode the spaced jets are directed away from said fluid receiving means, and venting means disposed on the far sides of the pair of jets for relieving fluid pressure in said receiving means and for receiving the jets in the second mode thereof. 4. The fluid control device set forth in claim 1 wherein said fluid receiving means comprises a single fluid receiving passage in alignment with said control means.

8. The fluid control device set forth in claim 1 wherein said fluid receiving means comprise first and second pairs of fluid receiving passages, said first pair of passages connected to a first common output passage, and said second pair of passages connected to a second common output passage for thereby providing a differential pressurized fluid output signal.

9. The fluid control device set forth in claim 1 wherein said first means comprises a pair of spaced nozzles adapted for communication with a common source of pressurized fluid.

10. The fluid control device set forth in claim 9 wherein said pair of nozzles are oriented in parallel relationship.

11. The fluid control device set forth in claim 9 wherein the centerline axes of said pair of nozzles are oriented in convergent relationship in the downstream direction.

12. The fluid control device set forth in claim 9 wherein the centerline axes of said pair of nozzles are oriented in divergent relationship in the downstream direction.

13. The fluid control device set forth in claim 9 wherein said control means comprises at least one nozzle posi tioned between said pair of spaced nozzles and adapted for communication with an analog source of fluid pressurized above ambient and variable in pressure in accordance with a selected variable characteristic to provide in said fluid receiving means an output fluid signal pressurized above ambient and variable in pressure proportionally to the pressure of the analog pressurized fluid source.

14. The fluid control device set forth in claim 9 wherein said control means comprises a single nozzle positioned midway between said pair of spaced nozzles and adapted for communication with a digital source of fluid intermittently pressurized in accordance with binary logic information to provide in said fluid receiving means a digital output pressurized fluid signal.

15. The fluid control device set forth in claim 1 wherein said control means comprises a single nozzle in alignment with the centerline axis of said device, said nozzle adapted for communication with a source of variable pressurized fluid.

, 16. The fluid control device set forth in claim 1 wherein said control means comprise a pair of spaced nozzles adapted for communication with a source of differential variable pressurized fluid.

17. The fluid control device set forth in claim 16 wherein said fluid receiving means comprise a plurality of fluid receiving passages connected to two output passages for thereby providing a differential pressurized fluid output signal in response to an input signal supplied flrorr the source of differential variable pressurized References Cited v UNITED STATES PATENTS 3,366,131 1/1968 Swartz 137-8l.5 3,416,487 .12/1968 Greene 137-81.5 X

M. CARY NELSON, Primary Examiner WILLIAM R. CLINE, Assistant Examiner 

